pi@raspberrypi /mnt/winbackup $ nmap -PN -p21 host

Starting Nmap 6.00 ( http://nmap.org ) at 2012-12-20 05:09 EST
Nmap scan report for host (66.152.109.61)
Host is up.
Other addresses for host (not scanned): 69.16.143.61
rDNS record for 66.152.109.61: 66-152-109-61.tvc-ip.com
PORT   STATE    SERVICE
21/tcp filtered ftp

Nmap done: 1 IP address (1 host up) scanned in 3.29 seconds